A new Jurassic paleomagnetic data and emplacementconditions study of the CAMP Gara Djebilet dykes (TindoufBasin, Southwest Algeria).

Abstract

International audienceThe Central Atlantic Magmatic Province (CAMP) is one of the largestidentified Mesozoic basalt provinces formed approximately 200 Ma ago as a preambleto the Pangea dismemberment. Recent 40Ar/39Ar dating and geochemical analyses ofdolerite sills and dykes and basalt lava flows in southwestern Algeria (Bechar area,Reggane, Hank and Tindouf basins) showed that these rocks are parts of the CAMP.These data represented good arguments to perform geological field observations andsampling for paleomagnetic and magnetic fabric (AMS) investigations in the Tindoufbasin CAMP formations. Three NE-SW oriented long doleritic dykes (198.9 ±1.8 Ma)in this basin were targeted in order to find out the structural context of theiremplacement (magnetic fabric) and to determine a new reliable Jurassic pole. Themagnetic fabric, in almost the whole sampled sections, is defined mainly by clusteringof k1 and k2 axes on the dyke plane whereas the k3 axis is nearly perpendicular to it.This fabric is therefore interpreted as due to magma flow. The new Jurassicpaleomagnetic pole, of a good quality, is very close to those obtained from coevaldetrital Algerian Saharan formations and those recently determined from coevalMoroccan igneous formations, it is also very close to the 200 Ma mean African pole.These results constitute a considerable contribution to a more precise knowledge of thegeodynamical context during this period